Enhanced coercivity of HCP Co-Pt alloy thin films on a glass substrate at room temperature for patterned media

High coercivity (H-c) Co-rich type Co-Pt alloy thin films with a columnar grain structure were deposited at room temperature (RT) by magnetron sputtering. Films with a thickness (t) of up to 10 nm had a FCC structure and exhibited soft magnetic properties. When t > 25 nm, the magnetic anisotropy changed from in-plane to isotropic. H-c was also enhanced with increasing t and found to be maximum at t=50 nm. The in-plane and out-of-plane H-c of the film was 2.2 and 2.7 kOe, respectively. Further increasing t. led to a slight decrease in H-c Microstructure and phase structure studies revealed columnar Co-Pt grains with a uniform lateral size grown on a 7 nm initial layer. Films with t > 25 nm showed a HCP phase, clue to the internal stress and volume effect. The microstructural details responsible for the enhanced RT magnetic properties of the HCP Co-Pt alloy thin films were investigated by TEM. (C) 2015 Elsevier B.V. All rights reserved.